The research investigated the effects of teaching aids on students' motivation to learn mathematics in day secondary schools in Rusizi districts. Specifically, the study identified the teaching aids that motivate students to learn mathematics in day secondary school in Rusizi districts, Rwanda, evaluated the level of student performance toward the use of teaching aids in learning mathematics in day secondary school in Rusizi districts, Rwanda, and examined the effects of using teaching aids and students' motivation to learn mathematics in day secondary school in Rusizi district, Rwanda. The population in this study consisted of 100 mathematics teachers with a sample size of 57 respondents, 50 head teachers, whose sample size is 28 respondents, and 162 students with a sample size of 67 respondents, with 175 as samples. To triangulate the data, primary sources were acquired utilizing questionnaires, interviews, and observation methods. To generate a sample population, the researcher used purposive sampling techniques to choose mathematics teachers and simple random sampling to choose students and headteachers. In data gathering and analysis, the study used both quantitative and qualitative methodologies in tandem. Content analysis aided qualitative data analysis, while quantitative data was presented using descriptive statistics (frequency, percentage, mean, and standard deviation) and inferential statistics (correlational and regression analysis) in the statistical package for social sciences. For the first objective, results indicate that 59.9% strongly agreed that the use of Geoboards in teaching indicates that they are being used as teaching aids. 96.6% strongly agreed that the use of algebra tiles in teaching and learning mathematics is indicated by the use of teaching aids, and 93.3% strongly agreed that the use of concrete materials in teaching and learning by teachers and students indicates that they are using teaching aids. 77.5% strongly agreed that place value blocks to teach numerical concepts for teachers are mathematics teaching aids. For the second objective, 84.3% strongly agreed that national examination results indicate their mathematics academic performance, 88.8% strongly agreed that homework completion indicates their mathematics academic performance, 67.4% strongly agreed that improved class participation indicates their mathematics academic performance, and 83.7% strongly agreed that the number of students above pass marks indicates their mathematics academic performance. Finally The study objective three revealed that the correlation and regression results established the existence of a positive correlation among the effects of using teaching aids and students’ motivation to learn mathematics in day secondary school in Rusizi district, Rwanda, where the Pearson's p-value and significance were justified by p-values less than 0.05, and the research results evidenced a positive correlation between the use of teaching aids and students' motivation to learn mathematics in day secondary school in Rusizi district, Rwanda. The study recommended that the government of Rwanda should allocate more instructional materials and training of mathematics teachers to enhance the use of the teaching aids in teaching and learning activities in Rwanda.